FIG. 1 shows a probe array 1 as known in the art. The array comprises a number of probes 2, connected by a base portion 3. Each probe comprises an elongate shaft portion 4 and a triangular chisel shaped tip portion 5, with micro-electronic structures 6 embedded in the shaft portions. The probes 2 of the array 1 have an essentially constant thickness, said thickness being the same for the shaft portions 4 and the tip portions 5. Said thickness corresponds to the thickness of the semiconductor substrate from which the probes are produced. The probe tips are thus formed by a straight edge 100 with a length that equally corresponds to said substrate thickness. This tip shape is not able to pierce through the brain membrane, also known as the Dura matter, without causing a harmful dimpling of the Dura.
Using thinner substrates or etching the probe tips to reduce the thickness leads to probes with insufficient mechanical properties to perform the required functions. Other techniques are known, such as anisotropic etching techniques which etch certain Si-planes faster than others. However, this is still a technically complex and time-consuming approach.
Overview
The disclosure is related to a method and probe arrays as described in the appended claims. The disclosure is thus related to a method for sharpening the tip of a microprobe, comprising, for example, the steps of:                providing at least one probe said probe having a base portion, an elongate shaft portion and a triangular chisel-shaped tip portion, at least said shaft and tip portions having an essentially constant thickness extending between a first and second surface of the probe,        providing a carrier having a first and second flat outer surface oriented at an angle to each other, so that said surfaces are joined by an edge of said carrier,        attaching the first surface of the probe to the second surface of the carrier, with the base portion and the majority of the shaft portion attached to said second surface and the tip portion being in close proximity to said edge,        subjecting the first surface of the carrier and at least part of the tip portion of the probe to a grinding step, to thereby remove material at least from said triangular, chisel shaped tip portion of the probe.        
According to an embodiment of the method, an array of said probes is provided, said array comprising a common base portion, and parallel probes extending outward from said base portion, at least the elongate shaft portions and chisel shaped tip portions of said probes having an essentially constant thickness extending between a first and second surface of the probe array, and the first surface of said array is attached to said second surface of the carrier, with the base portion and the majority of each shaft portion attached to the second surface, and the triangular chisel shaped tip portions being in close proximity to the edge, and wherein material is removed from the triangular tip portions of all of said probes.
According to an embodiment, at least part of said triangular, chisel shaped tip portion(s) is (are) extending outward from said edge, so that said part of the triangular tip portion(s) extend(s) below the first surface of the carrier when said first surface is held horizontally, and wherein substantially no material of the carrier is removed during said grinding step.
According to another embodiment, the probe(s) do(es) not extend outward from the edge, and wherein the carrier material and the probe tip material are removed simultaneously during said grinding step.
Said edge may be shaped as a straight line. Said probe(s) may be placed perpendicularly to said edge.
The location on the carrier block onto which the probe(s) is (are) attached may be provided with an alignment structure. Said alignment structure may comprise one or more grooves into which said probe or probes may be placed. Said alignment structure may be a negative imprint of the probe or probe array.
According to an embodiment, the grinding step is done by placing the carrier on a rotating grinding disc and applying pressure on the carrier. The grinding step may be followed by a polishing step.
According to an embodiment, the grinding step is continued so as to obtain a sharp pointed tip, lying in the plane defined by the second surface of the probe or probe array.
According to another embodiment, the grinding step is followed by the steps of:                attaching the second surface of the probe or probe array to the second surface of the carrier, with the base portion and the majority of the shaft portion of each probe attached to said second surface and the tip portion being in close proximity to said edge,        subjecting the first surface of the carrier and at least part of the tip portion of the probe(s) to a grinding step, to thereby remove material at least from said triangular, chisel shaped tip portion(s) of the probe(s), so as to obtain a sharp pointed tip lying in between the planes defined by the first and second surface of the probe or probe array.        
According to an embodiment, the grinding step is done with a grinding surface having an average grain size between 5 μm and 20 μm.
These as well as other aspects, advantages, and alternatives, will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference where appropriate to the accompanying drawings.